The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The present teachings relate to packet routing for a mobile access terminal moving between two access nodes.
In wired IP networks, a client and a server identify and communicate with each other using each other's Internet Protocol (IP) address. Every IP packet carries the sender's IP address (source IP address) and the recipient's IP address (destination IP address). Intermediate routers and switches look at the source/destination IP addresses to route packets from source to destination. Methods to route packets based on IP addresses in a packet are well known. Typically, the client's IP address is either permanent or dynamically assigned. In either case, the address is decided by an address manager server typically known as a DHCP server and all clients within a subnet share a fair bit of commonality in their address.
In effect, this creates a hierarchy of how addresses are managed and administered and is done with a view towards helping routing and forwarding processes that process IP addresses. However, in wireless networks, mobile clients, or access terminals (ATs), move around and do not initiate sessions from the same locations. One could argue that every time an AT moves from one access point (AP) or base station to another, then the IP address changes. This creates two problems: first, changing IP addresses for ATs is not easy; and second, routers need to somehow be updated with the new address so that packets from a server, also referred to as a Correspondent Node (CN), for the same mobile AT can now be routed differently.
These problems are addressed by the so-called MobileIP standards and protocols, which provide a framework for accomplishing IP address management and routing for mobile ATs. The basic idea is to have a “home address” (HoA) that does not change for the mobile AT, and to additionally have a “care of address” (CoA) that is related to the location of the AT (typically based on the access network's IP address). The CoA is allowed to change when the mobile AT moves from one node to another. In this framework, the HoA and CoA are “bound” to each other using Mobile IP protocols, e.g., MIPv4, MIPv6, etc., at a home agent (HA), which knows both the CoA and the HoA of the mobile and maintains the binding relationships. Hence, when a CN sends a packet to a mobile AT, the packet is routed through the HA which, in turn, sends the packet to the access network or node at which the mobile AT is currently located. Generally, there are two types of mechanisms to assign the CoA. The first method uses a CoA that is located in the network, for example, the CoA of every mobile AT attached to a given access network element, e.g., a PDSN, could be equal to the IP address of the PDSN. In the second method, the mobile AT generates its own CoA based on the network prefix of the access network or the mobile AT is assigned a specific CoA by the access network. This method of generating a CoA is often referred to as a Co-located CoA or (C-CoA).
However, when using a C-CoA for the mobile AT, handoff cannot be managed entirely by the access network. That is, the C-CoA is calculated by the mobile AT and has to be registered at the HA. Generally, the C-CoA is calculated based on a network prefix of the access network and a permanent identifier that is specific to the mobile AT. Typically, the network prefix is obtained through a router advertisement from the access network element that mobile AT is anchored with, e.g., a PDSN.
Generally, there are two types of mobile IP protocols, i.e., terminal based client mobile IP (CMIP) and network based proxy mobile IP (PMIP). In CMIP all the binding relationships are initiated by the mobile AT, while in PMIP all the binding relationships are initiated by network elements on behalf of the mobile AT.
In client mobile IP (CMIP), interactions involve the mobile AT, a home agent (HA), an authentication, authorization and accounting (AAA) infrastructure, and possibly a gateway in a network, such as a packet data service node (PDSN). Typically, establishing a CMIP session, given the number of interactions and network elements, is “slow” and may take anywhere between a few 10's of milliseconds to a few 100's of milliseconds. In proxy mobile IP (PMIP), since mobility management is done by the network, establishing PMIP sessions can be significantly faster. However, in order to establish PMIP sessions, security issues have to be addressed.